House tabs speed

[Damian Jay]

I wasn't sure where to ask my question so I've popped into the general topic.

 

House tabs - I was wondering what is a general speed that house tabs fly out / in - how many feet per second to they raise / lower and is the speed dependant on how far they have travel?

 

 

So I'm asking a few general questions relating to house tabs:

 

- How fast / slow do your venues house tabs raise or lower?

- Is the speed variable? (when I worked at the Kings Theatre in Southsea many years ago, there were two of us on the house tab winch, we had 35 turns each on our own with both of us doing the middle 12 turns. 82 turns of the winch to fly out completely)

- What do you consider a reasonable speed?

 

The reason behind my ponderances .... I was attempting to work out what speed I'd need a motor to run at to fly out / in a set of house tabs on a model theatre. Then I realised that I don't generally have a clue what an appropriate speed would be.

As my local theatres are currently closed :-( this is the perfect place to ask.

 

Thank you for any information you are happy to share :-)

[IRW]

I don't think I've ever worked at, or toured to a venue where the house tabs are on a winch, or indeed fixed speed, so to answer your questions:

- How fast / slow do your venues house tabs raise or lower?

As fast as artistically directed, and/or dependent on the skill/strength of the flyman. I've worked on some shows where the brief to the flyman is 'how quickly can you physically get them in", and a few where the direction was 'as slow as possible'...!

 

- Is the speed variable?

Yes. See point 1.

 

- What do you consider a reasonable speed?

Again, see point 1...!

I was attempting to work out what speed I'd need a motor to run at to fly out / in a set of house tabs on a model theatre.

 

Why not wire it such that you can vary the speed of the motor?

Edited January 1, 2021 by IRW

[Damian Jay]

 

 

Why not wire it such that you can vary the speed of the motor?

 

Truthfully, I was hoping to be a little lazy and find out a decent speed of movement that could be scaled down to a model size. Then just find a motor that moves at that speed.

 

 

The reality of converting RPM to feet per second is proving to be a challenge for my mathematically challenged brain. When the local college is open again I can go chat to one of the engineering lecturers.

As for wiring up a speed control to vary the speed .... that may be beyond me for a good while yet.

 

 

 

[TomHoward]

How does the model winch work from the motor? You could keep the motor RPM and change the winch drum size to change speed..

 

As a middle ballpark I’d say they should take in the region of 5-6 seconds to fly out (although ours swipe sideways & open on a track). You could then work your speed out from the distance and time..

 

Oh - that said though they probably close faster than they open, although they may sometimes close in a blackout after the bows, if that covers not needing a change in speed.

[ontoprigger]

As others have said the speed is usually variable and has some form of artistic element to it.

But to give you the speed of the winch Multiply the diameter of the drum by pi, which is approximately 3.142, This is the object's circumference. Multiply the circumference by the motors output speed (angular speed), measured in rpm. Divide this by 60 to give you the distance per second. For example if you have a 100mm drum and a shaft speed of 100rpm, then that's 0.1 X 3.142 = 0.03142 X 100/60 = 0.523m/s.

If this were a real winch you would need to calculate the size of the motor to the load to be lifted, but I guess for the model you can probably get away with using what's available as the choice of smaller motors is probably going to be speed driven.

It should be relatively easy to buy a variable speed control, they are available for model cars and trains.

[sandall]

When doing a (on the cheap) refurb on a local town hall a few years ago I put in a cinema motor which IIRC takes about 8" to close a 10m wide proscenium, which seemed a good compromise speed (another local town hall had tabs so fast they could sweep a small child off the stage !!).

[Jivemaster]

Personally the speed of the tabs is a major part of the art of the performance, so some can be fast and some can be slow.

[pscandrett]

Also, if you want to get really nerdy, there's a definite acceleration and deceleration curve to think about - with large tabs coming in, it can take quite a bit of oomph to get them going and similar effort to slow them down to hit the deck without a bounce, so a straight go/stop on a motor isn't going to look realistic at all. You can probably model this mechanically with a non-cylindrical axle on your motor, or programmatically with a stepper motor, or no doubt there's an analogue equivalent too.

[sunray]

My big bugbear with AmDram is no matter how much you tell the puller over the intercom to be quicker they never ever speed up. One of our guys takes about 20 seconds to pull a 6m [yes 2x3m] on a horizonal track.

[mnorwood]

My big bugbear with AmDram (and dance schools) is that you have to repeatedly remind certain folks to pull smoothly - instead they yank at the rope causing the curtains to move in abrupt start-stop motions. Appearances aside, it probably isn't good for the rope/pulley system.

 

More on topic: at a different venue the (horizontally opening) house curtains are motorised, and run at a fixed speed. No acceleration or deceleration - they start and stop abruptly. The venue's tech spec claims that the prosc opening is 7.3 metres (~24 ft) wide (so with overlap with each other and the prosc arch itself each side probably runs roughly 4m (~13ft)). I've never timed how long they take to fully open or close, but estimate from memory somewhere between four and six seconds. (I realise the OP was asking more for vertically opening tabs, but just as comparison...)

Edited January 2, 2021 by mnorwood

[paulears]

When people consider speed they forget that the appropriateness depends on travel height. So when a fast reveal is needed on a tall stage pros opening, fast me and VERY fast, while fast on a letterbox stage is quite slow by comparison. Initial acceleration to get them going might need a leap in the air and 15 stones of assistance. Absolute worst is single speed motor the absolute worst, never doing it right ever. Best is a skilful strong person and the best motor drive is nearly as good. In a model, mechanical motor and train set controller, but that was in 1969.

[TomHoward]

Another possible idea for a model is the Sail winch servo types - made for model boats to wind ropes in & out. They’re like a servo but generally 1-6 turns with a drum on.

[sunray]

How big is the model?

 

I've been imagining a travel of something around 200mm, the requirements for which will be very different for something of 1m

 

[Damian Jay]

Wow, a lot of info there thank you.

And a big thank you to @Ontoprigger for the formula :-)

 

The point about the acceleration and deceleration of the tabs is fantastic and one that I hadn't thought about.

 

The proscenium opening is based on the size of A3 paper (as that's the largest printer I have for printing the scenery that I can't make)

A3 size is 420 mm x 297 mm in portrait mode.

 

Allowing for tabs overlap at the sides of the proscenium (10 mm per side) .. the size drops to 400mm width

And allowing for the overlap at the top of the pros of 17mm

 

So at scale 1:25 my pros opening will be 400mm wide by 280 mm high = 10m wide by 7m high

(the tabs actual size would be 420 mm x 297 mm at 1:25 scale and 10.5m wide and 7.42m high at 1:1)

 

@Tom Howard - I don't have a winch drum as such, I was planning on attaching a long shaft onto the shaft of the motor. This would run longer than the pros opening and up in the flytower. I would then attach my fly lines (probably 3 lines) to this shaft at the appropriate place. As the shaft rotates it would wind the lines up round it raising the tabs. When changing direction the lines would unroll and lower the tabs.

 

The shaft of the motor is 2.5 mm diameter, so the shaft I would fix onto that would probably be around the 4.5 mm or 5mm diameter mark.

 

Your tip on sail winches I am looking into as well. Thank you

 

@Ontoprigger - I like the idea of variable speed control..... that would give me options for a faster IN, and would also (hopefully) give me the the slightly slower start to the fly OUT and the slowdown of the IN to avoid bounce.

 

I'm hoping I can find a way to rig up and control the motors via DMX and set up a profile for the motors in my DMX program. that way I can 'play' with speeds and program them for each production. Not yet sure if making a motor DMXable in miniature is possible. More research is needed on this.

 

Hope the above info was helpful.

Edited January 2, 2021 by Damian Jay

[sunray]

Wow, a lot of info there thank you.

And a big thank you to @Ontoprigger for the formula :-)

 

The point about the acceleration and deceleration of the tabs is fantastic and one that I hadn't thought about.

 

The proscenium opening is based on the size of A3 paper (as that's the largest printer I have for printing the scenery that I can't make)

A3 size is 420 mm x 297 mm in portrait mode.

 

Allowing for tabs overlap at the sides of the proscenium (10 mm per side) .. the size drops to 400mm width

And allowing for the overlap at the top of the pros of 17mm

 

So at scale 1:25 my pros opening will be 400mm wide by 280 mm high = 10m wide by 7m high

(the tabs actual size would be 420 mm x 297 mm at 1:25 scale and 10.5m wide and 7.42m high at 1:1)

 

@Tom Howard - I don't have a winch drum as such, I was planning on attaching a long shaft onto the shaft of the motor. This would run longer than the pros opening and up in the flytower. I would then attach my fly lines (probably 3 lines) to this shaft at the appropriate place. As the shaft rotates it would wind the lines up round it raising the tabs. When changing direction the lines would unroll and lower the tabs.

 

The shaft of the motor is 2.5 mm diameter, so the shaft I would fix onto that would probably be around the 4.5 mm or 5mm diameter mark.

 

Your tip on sail winches I am looking into as well. Thank you

 

@Ontoprigger - I like the idea of variable speed control..... that would give me options for a faster IN, and would also (hopefully) give me the the slightly slower start to the fly OUT and the slowdown of the IN to avoid bounce.

 

I'm hoping I can find a way to rig up and control the motors via DMX and set up a profile for the motors in my DMX program. that way I can 'play' with speeds and program them for each production. Not yet sure if making a motor DMXable in miniature is possible. More research is needed on this.

 

Hope the above info was helpful.

There are many versions of LED DMX dimmers available and I see no real reason they cannot be utilized but off the top of my head I think it may need 2 channels, one for speed and the 2nd for direction.

The fly lines will need to over some guides or pullies to control the position or else the tabs will travel acros the stage as the line winds along the shaft.

I think you will also require end switches.